missing (former implicit) linking to libm. And as implicit linking can be dangerous,
this changed, see: http://fedoraproject.org/wiki/Features/ChangeInImplicitDSOLinking

Commited by Ingvar. This is necessary to make varnish build on fedora>13.



git-svn-id: http://www.varnish-cache.org/svn/trunk/varnish-cache@4712 d4fa192b-c00b-0410-8231-f00ffab90ce4